Control apparatus



Nov. 2l, 1950 w. H. KLlEvER CONTROL APPARATUS Filed NOV. 9, 1944 En S wz Patented Nov. 2l, 1950 lUNITED STATES PATENT OFFICE coNTnoL APPARATUS Waldo H. Kliever. Minneapolis, Minn., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware yApplication November 9, 1944, Serial No. 562,679

(Cl. 23d-78) 3 Claims.

f properties of each type of electrical energy which make it especially adapted to particular applications are familiar to electrical engineers. For example, alternating current makes possible the use of transformers to increase and decrease voltages, and permits the performance of all functions which depend for their operability on phase relationships. This, on the other hand, is a disadvantage for some applications where,

f for example, it may be desired that voltages from A a number of sources be added, exerting each its prone!l influence in the total voltage; the phases of alternating voltages to be so added must be accurately known if the addition is to be a success, and as a result the process is much more complicated than the addition of unidirectional s voltages.

Numerous attempts have beeny made to ilnd ready means for converting signiilcant potentials 'from one form of energy to the other. In converting A. C. to D. C., the rotary converter and the electronic rectifier are familiar examples of structures having this intent and adapted for use in power applications, while the crystal detector and the diode detector are examples of the same sort of device adapted to communications use.

The fact remains, however, that no completely satisfactory method of converting one form of electrical energy to another has heretofore been f developed. Most devices of this sort are unduly complicated by the necessary consideration of phase in alternating currents, and the expedients thus far resorted to introduce spurioussignals which may be of considerable significance for accurate work, even to the extent of prohibiting the usel of such devices where extreme accuracy is required.

There are also occasions where it is desired to actuate an electric motor, particularly desirable because of its characteristics when energized with alternating current, under the control of a'. member operating most satisfactorily when energized with direct current. `lilir example, it may be desirable to control a reversing motor, which most conveniently' comprises a split-phase motor operated by alternating current, in accordance withthe electrical output of a thermocouple which is, of course, unidirectional. Means have not heretofore been avail-A able for accomplishing this with satisfactory accuracy and simplicity.

My invention is directed to the solution of problems of the nature just outlined. by the use of an electron discharge device of a generally new and improved means for converting a unidirectional signal into an alternating current power response which reverses in phase and varies in amplitude with reversal in polarity and change in magnitude of the unidirectional signal.

A further object of my invention is to provide new and improved means for controlling an alternating current motor from a direct current signal.

Various other objects, advantages, and features of novelty which characterize my invention are pointed out with particularity in the claims annexed hereto and forming a part hereof, However, for a better understanding ofthe invention, its advantages, and objects attained by its use, reference should be had to the subjoineddrawing, which forms a further part hereof, and to the accompanying descriptive matter, in which I have illustrated and described a preferred embodiment of my invention.

In the drawing, the single ilgure is a diagrammatic showing of my invention as applied to the control of the temperature in a space.

Construction In the drawing I have shown a space il, to be heated, which may be enclosed by any suitable wall il and may comprise for example an oven, a heat-treating chamber, or a furnace. The space may be heated by any suitable burner, not shown, which is adapted to be supplied with liquid or gaseous fuel through a conduit I2 under the lcontrol of a valve I3. Valve Il is actuated by a in quadrature, motor Il operates in a forward or reverse direction. depending on whether the current in winding 3| leads or lags -that in winding 22: this Practice is familiar to those skilled in the art.

In general, motor I4 is controlled by an ampliiler I5 whose input signal comes from an electron discharge device |1, the latter being controlled in a manner to be later described by a thermocouple located in chamber Il. The cold .lunction for thermocouple 2l is located in a temperature stabilized chamber according to the needs of the application in which my circuit is to be used, the temperature of this chamber may be thermostatically regulated, or thechamber may simply be insulated to provide a stabilizing heat reservoir surrounding the cold junction.

Alternating current of a power frequency is provided fo; energizing ampliiler i5, motor I4, and discharge device I1 through a pair of conductors 2| and 22, the latter including a main switch i9. The electrical energy is distributed in part by a transformer 22 having a primary winding 24 and a plurality of secondary windings 25, 25, and 21.

Amplifier i6 is connected with discharge device i1 through a transformer 25 having a secondary winding 31 and a primary winding 25 having a center t 4l).

For providing energizing voltages for electron discharge device 'i, I have shown a power source 4| comprising a plurality of batteries 42, 44, 45, and 4G. An independent battery 42, and a potentiometer 83 comprising a resistance winding ductor 15 to'create' 82 and a contactingI slider 8|, are also provided:

this battery and the resistance winding are connected in parallel. It will be understood that power source 4| need not necessarily comprise batteries, but that a suitable source of rectied and filtered A. C. may be used for'this purpose.

Electron discharge device l1 is shown to comprise an envelope 50 enclosing a pair of anodes 5| and 52, a pair of detiecting plates 52 and 54, an accelerating electrode 55 electrically connected with deflecting plate 54, a focusing electrode 55, a control grid 51, a. cathode 58, and a cathode heater 59. A pair of defiecting coils 41 and 45, connected by a conductor 45, are coaxially mounted outside the tube, their common axis Ybeing parallel to plates 52 and 54 and intersecting the axis of the tube.l

Operation The operation of the structure just recited will now be described. In the inoperative condition of my system, target plates 5| and 52 are maintained at a positive potential with respect to cathode 52 by batteries 44, 45, and 45, which are connected in series. The circuit may be traced from cathode 58 through conductors 55 and 54, batteries 44, 45, and 45 in series, and conductor 12, to center tap r4|) of secondary winding 25. From here a pair of paths may be traced, one through the `left hand portion of winding 25 and conductor 14 to plate 52 and the other through the right hand portion of winding 25 through conductor 13 to plate 5|.

Control grid 51 is maintained at a negative potential with respect to cathode 55 by means of battery 42. The circuit maybe traced from cathode`55 through conductors 55 and 64, secondary winding 25 ,of transformer 22, conductor J2, battery 42, and conductor 52 to control grid 51. The focusing electrode 55 is maintained at a positive potential with respect to cathode 5l by battery 44. The circuit may be traced from cathode v258 through conductors 55 and 64, battery 44, common terminal 55 between the positive terminal of battery 44 and the negative terminal of battery 45, and conductor l1, to focusing electrode 54.

The accelerating electrode 55 is maintained at a positive potential with respect to cathode 5l by batteries 44 and 45, which, as has been pointed out, are connected in series. The circuit may be traced from cathode 5l through conductors 45 and 54, batteries 44 and 45, the common terminal 1l between the positive terminal of battery 45 and the negative terminal of battery 4l, and conductors 1| and 55 to electrode 55.

Deflecting plate 52 is maintained at a negative unidirectional potential with respect to detlecting plate 54 and accelerating electrode 55 by a voltage derived from battery 42 through potential divider l2. The circuit may be traced from accelerating anode 55 through conductors 55 and I4, the right hand portion of winding I2 of potential divider 82, slider 8|, fiecting plate 52.

Thermocouple 2,0 may be of any conventional type and may comprise, for example, a first conductor 15 -of iron and a second conductor 15 of constantan. At the cold junction 2l, conductor 16 is connected with deilecting coil 41 through conductor 18, while conductor 15 is connected with deilecting coil 45 through conductor 1l.

Thermoelectrically generated current therefore flows in coils 48 and 41 from conductor 15 to cona magnetic iield traversing tube parallel to the coil axes: as is well known to those skilled in the art, this results in deflection of the electron beam ln a plane at right angles to the direction of the held, that is, from plate 5| to plate 52 or vice versa, depending on the direction of winding of the coils.

Assuming that my system is to be set into operation, it will be understood that in the absence of any nre in chamber Il, my system must operate in such fashion that valve I2 is wide open to permit the passage of fuel to the burner. To

set my system into operation valve 5 is manually opened to permit the passage of fuel to the burner, and a fire is started in the chamber. At the same time, main switch I5 is closed energizing primary winding 24 of transformer 22, as well as input terminals '88 and 55 ot amplifier l5, from conductors 2| and 22. By transformer action an induced voltage appears in secondary winding 24 of transformer 22, energizing cathode heater 52 through conductors $4 and 5I. When heater 5! reaches a suitable temperature, electron emission from cathode 58 takes place, due to the presence of the positively charged plates 5| and 52 spaced from the cathode 55. Due to the action of focusing electrode 55 and accelerating electrode 55, a beam of electrons passes from cathode 5B between deilecting plates 52 and 54 and is directed toward plates 5| and 52.

Energization of primary winding 24 at the same time induces an alternating voltage in secondary winding 25 of transformer 22, which results in a potential. difference being impressed between cathode 55 and control electrode 51 which is superimposed on that provided by battery 42. It will be recalled that in the circuit traced above between the cathode and control electrode 51, the secondary winding 25 and the battery 42 are connected in series. The combined eil'ect of the voltages from secondary windings 25 and battery 44 is to modulate the electron beam in intensity, the amplitude `of the modulation being determined by the voltage derived from winding 25 and the constant value of intensity about which and conductor 11 to de- Y the modulation takes place being determined by battery 43.

The electron beam emitd from accelerating anodellisdirectedaxiallyoftheenvelopeso that in the absence of other forces the beam is of substantial sise and impinges equally on plates Il and l2. However, the beampasses between deecting plates I3 and 54, the former of which may attract or repel the beam depending on the polarity of battery 42 and on the setting of slider Il, and also through the held of coils 41 and 4I, which has a further deecting effect on the beam, depending on the magnitude of the thermoelectric current owing in the coils. Since the current output of a thermocouple of this type, 'for any temperature differential to which it may be exposed, is known, it-is possible to arrange for operation of the furnace or oven at any desired temperature by adiusting slider Il to derive from battery 42 a voltage equal in deflecting effect on the beam, to the thermoelectric current of thermocoupie at the desired temperature. Slider 3i may operate a pointer 33 moving over a scale 35 graduated' either in units of voltage or in units oftemperature corresponding thereto to indication of operation of the device.

In initiating operation of mysystem, the user sets slider 3i so that the pointer indicates the desired temperature, and the system is ready to operate. Unless the temperature in the space is already that desired, the deflection of the beam due to the voltage between plates 53 and 54 is not exactly counteracted by the deflection due to current in coils 41 and 43. Suppose the coils are so wound that increasing thermoelectric current acts to increasingly deflect the beam toward plate BI. Since the temperature in the space is too low, the deflective effect of the plates predominates, and a resultant deflection of the electron give an J beam from its central direction takes place so that it no longer impinges equally upon targets '5I' and 52. Since plate 53 is negative with respect to plate 54, the negative beam of electrons is repelle'd so that it impinges more on plate 52 and less on plate 5|. Opposite winding of the coils, or opposite connection of the thermocouple, would require a reversal of the polarity of battery 42.

Anode current flows in conductors 14 and 13 in proportion tothe relative impingement of these plates, by the electron beam. Since these currents are derived from batteries 44, 45, and 46, and since .they flow in opposite directions through Isecondary winding 38 from center tap 43, it is evident that unless the anode currents are equal the flux set up in the core of transformer 35 by the first current is not equal to the opposing flux set up by the other current, and there is a, residual effective flux which induces anA output voltage from secondary winding 31 of the transformer. The `residual flux may be of a rst time-phase relationship or in 180 degree phase relationship therewith, depending upon which anode current predominates. The induced, voltage in secondary winding 31 issubject to the same phase reversal, and is impressed upon the input terminals 31 and Il of amplifier I6 by conductors 3| and 92.

Energization of transformer 23 induces a potential in secondary winding 21 of the transformer, and this potential is rimpressed across field winding 3l of motor I4 through ground connections 96 and 35 and conductor 31, condenser 33, and conductor 43. In the same way, the output voltage from amplifier It is supplied to field winding 32 of motor i4 through conductors 33 e. andtl: thecondenseruis winding 32 to bypass harmonics ofthe'operating frequency. f

since the details of such an amplifier arey not essential to an understanding of my invention, the structure of the amplifier is not specifically illustrated here. The anode currents flowing in conductors 'I3 and 14 are in 180 phase relation with one anotherand with the modulating voltage derived from secondary winding 2l. The voltage across secondary winding 31 of transformer 3s is therefore in phase with or 180 degrees out of phase with the modulating voltage. depending on which anode current is the larger. The voltage across field coil 32 is likewise in phase or 180 degrees out of phase with the modulating voltage because of the properties of the amplifier just set forth. The current in ileld winding 32 lags the voltage across it by degrees as is well known to those skilled in the art.

The current through condenser 33 and field winding 3| is substantially in phase with the voltage across secondary winding 21. This is because the capacitance and the inductance of these members have been so chosen that the circuit is resonant at the frequency of the source, and the circuit presents only a resistive aspect to the secondary voltage. Since the voltages across windings 25 and 21 are in phase, and since the current in winding 3| is of the same phase, while that in winding 32 is leading or lagging by 90, motor 30 is energized to rotate in a first direction if the beam impinges principally on plate 52 and in a second direction if the beam impinges princlpally on plate 5|.

Under the starting conditions the. temperature of space III is less than that desired and accordingly the deflective eilect of the plates exceeds that of the coils. The electron beam therefore impinges principally upon plate 52 and the anode current in conductor 14 exceeds that in conductor 13. The induced voltage in 31, when transf mitted through amplifier I3. is such as to cause operation of motor i4 in a first direction so as to open valve I3 if it is not already so wide open as to operate a conventionalr limit switch which is preferably used in conjunction with my invention,

but which is not illustrated in the drawing forthe sake of avoiding confusion.

Continued operation of the burner, in space ill results in a rise in the temperaturein the space. to which thermocouple 20 responds by anincreased current output. The deflective effect of coils 41 and 43 therefore increases,fwhile that of plates 53 and 54 remains the same: accordingly the deflection of the electron beam from its central position decreases. When the temperature in space i0 has reached a desired value, .the deective eil'ects of the plates and the coils are exactly equal and opposite, they electron beam impinges equally upon plates '5i and 52, and there is no induced voltage in secondary winding 31 of transformer 35.

motor stops.

If due to lag between the operation of the field Field winding 32 of motor I4 is therefore not energized, and operation of the assoms I 7 central position so that it impingcs more upon plate si than upon plate I2. Greater anode current flows in conductor Il than in conductor 14 and current nows in field winding 32 which is of the opposite phase to that ilowing in the ating shaft of valve H and the slider Il of potentiometer 33 so that as the valve is actuated by motor I4 the potentiometer arm is simultaneously moved to change the potential of plate Il with respect to plate 8l. The mechanical connection between the valve and the slider, and the resistance increment of winding 82 per unit of travel of the slider, are such that when the slider has moved along the winding to where the electrostatic deflection of the electron beam is equal to and opposite the electromagnetic deilection. suiiicient change in the position of valve il has taken place to change the temperature in space I0 by the desired amount, by altering the now o! fuel to the burner. If mechanical connection I8 is provided, it will be appreciated that a manual setting of slider 8i at the time of initiating operation of the device will no longer be necessary since, at the time the burner was last turned oi! and the temperature in the chamber fell to room temperature, operation of the system to maintain its balance naturally moved the slider to the starting position and opened the automatic valve I3 in preparation for a new cycle of operation.

Numerous objects and advantages oi my invention have been set forth in the foregoing description together with details of the structure and function of the invention, and the novel features thereof are pointed out in the appended claims. The disclosure, however. is illustrative only, and I may make changes in detail. lparticularly in matters of shape,` size, and arrangement of parts within the principle'of the invention, to the full extent indicated by the broad and general meaning oi' the terms in which"` the appended claims are expressed.

I claim as my invention:

l. In a device of the class describedin combination, an electron discharge device comprising means directing a beam ot electrons along a normal axis to comprise a beam current, independent electrostatic and electromagnetic defiecting means, a plurality oi' anodes spaced about said axis for impingement by said beam, means energizing said device, means modulating the intensity of said beam at a,selected i'reo uency, thermoelectric signal generating means responsive to the temperature in a space, means connecting said generating means to said electromagnetic deecting means, whereby to deiiect said beam from said axis to vary the diiIer-' ential impingement of said beam upon said anodes. an amplifier, a motor controlied'by said amplier, means associating the anode currents 8 ofsaiddischargedevicainopposed relatiomwith said ampliiler, whereby to'control the operation o! said motor, and means actuated by said motor forcausingachangeinthetemperatureoisaid spaceoppositetothatcausingsaidresponseos said generator, a standard source o! electrical energy. and means actuated by said motor for variably energizing said electrostatic deiieeting means from said standard source in opposition to said thermoelectric energisation o! said ilrst deiiecting means.

2. In a device oi' the class described. in conibination: a source of alternating current o! a selected frequency: a motor deslgnedfor operation by means of alternating current o! said irequeney; an amplifier for controlling operation of said motor; an electron discharge device including a plurality of anodes and means directing a beam of electrons along an axis passing between said anodes, so that said beam normally impinges equally upon said anodes to comprise equal' anode currents; means including said source for modulating the' intensity of said beam at said frequency, whereby tol impart to said anode currents componentsof saidirequency; electrostatic and electromagnetic means i'or defiecting said beam from said axis, whereby to destroy the equality oi' said anode currents; a thermoelectric signal generating member re'- sponsive to the temperature in a space; means connecting said member to said electromagnetic deilectingfmeans; means associating the anode currents of said discharge device, in opposed relation, with said ampliiler to cause reversible yoperation of said motor, a voltage source, and

means energizing said electrostatic defiecting means from said source in accordance with operation ci said motor.

3. In a device oi' the class described, in comt bination: a plurality of anodes; means directing a beam of electrons along an axis passing bctween said anodes so that said beam normally impinges equally upon said anodes to comprise equal anode currents; means modulating the intensity of said beam at a selected frequency. whereby to impart to said anode currents alternating components 'ot said frequency; a motor ydesigned for operation by means of alternating current of said frequency; electromagnetic means for deilecting said beam from said axis,

whereby to destroy'the equality o! said anode currents; means utilizing any inequality between said anode currents to cause operation oi' said motor in a sense dependent on the sense of said inequality; and electrostatic means actuated by said motor i'or causing said beam to return to its undeilected position.

WALDO H. KLIEVEH..

nsraasNcss crran The following references are, of record in the ille ot this patent:

UNITED STATES PATENTS 

